You don't need any weapons than the ones you already have. Although, I probably would stop using any Weapons with Stonestrike.
There are two methods to this fight, one that defeats the Negator, or one that does not. Let's assume that you do not have Slow.
If you decide NOT to destroy the Negator, then simply keep Auron, Tidus, Kimahri, or Wakka on the front lines. Or Rikku if you feel like Stealing (not that it gives you anything good, but the Lightning Gems you can steal can be used against it). Heal with Potions/Hi-Potions as necessary.
If you DO decide to destroy the Negator, you will have magic. Not the world's best trade if it not for Ixion or Ifrit. When you destroy the Negator, get Yuna into the fight. There begins a countdown to when the Crawler uses Mana Beam (turn "1"), so when it becomes the Crawler's turn, and it can use Mana Beam, use an Aeon to Shield. Ixion and Ifrit can heal themselves, so do not use Thundara/Fira on the Crawler, and instead, use this method to heal your Aeons. You can also continue the fight with an Aeon in place the entire time, relying on Black Magic to heal your Aeon, and using Aeon Overdrives (Thor's Hammer is the Keeper of the Pwn).